The nonmetallocene catalyst, also called as the post-metallocene catalyst, was discovered in middle and late 1990's, whose central atom involves nearly all of the transition metal elements. The nonmetallocene catalyst is comparative to, or exceeds, the metallocene catalyst in some aspects of the performance, and has been classified as the fourth generation catalyst for olefin polymerization, following the Ziegler catalyst, the Ziegler-Natta catalyst and the metallocene catalyst. Polyolefin products produced with such catalysts exhibit favorable properties and boast low production cost. The coordination atom of the nonmetallocene catalyst comprises oxygen, nitrogen, sulfur and phosphor, without containing a cyclopentadiene group or a derivative thereof (for example, an indene group or a fluorene group). The nonmetallocene catalyst is characterized in that its central atom shows comparatively strong electrophilicity and has a cis alkyl metal type or a metal halide type central structure, which facilitates olefin insertion and σ-bond transfer. Therefore, the central atom is easily subject to alkylation, and therefore facilitates formation of a cationic active center. The thus formed complex has a restricted geometrical configuration, and is stereoselective, electronegative and chiral adjustable. Further, the formed metal-carbon bond is easy to be polarized, which further facilitates homopolymerization and copolymerization of an olefin. For these reasons, it is possible to obtain an olefin polymer having a comparatively high molecular weight, even under a comparatively high polymerization temperature.
However, it is known that in the olefin polymerization, the homogeneous phase catalyst suffers from such problems as short service life, fouling, high consumption of methyl aluminoxane, and undesirably low or high molecular weight in the polymer product, and thus only finds limited use in the solution polymerization process or the high-pressure polymerization process, which hinders its wider application in industry.
Chinese patent Nos. 01126323.7, 02151294.9 and 02110844.7, and WO03/010207 disclose a catalyst or catalyst system finding a broad application in olefin polymerization. However, the catalyst or catalyst system should be accompanied by a comparatively high amount of co-catalysts, to achieve an acceptable olefin polymerization activity. Further, the catalyst or catalyst system suffers from such problems as short service life and fouling.
It is normal to support the nonmetallocene catalyst by a certain process, so as to improve the performance of the catalyst in the polymerization and the particle morphology of the polymer products. This is reflected by, moderate reduction of the initial activity of the catalyst, elongation of the serve life of the catalyst, alleviation or elimination of caking or flash reaction during the polymerization, improvement of the polymer morphology, and increase of the apparent density of the polymer, thus extending its use to other polymerization processes, for example, the gas phase polymerization or the slurry polymerization.
Aiming at the catalysts of the Chinese patent Nos. 01126323.7, 02151294.9 and 02110844.7, and WO03/010207, Chinese patent application Laid-Open Nos. CN1539855A, CN1539856A, CN1789291A, CN1789292A and CN1789290A, and WO2006/063501, and Chinese application patent No. 200510119401.x provide several ways to support same catalyst on a carrier so as to obtain a supported nonmetallocene catalyst. However, each of these applications relates to the technology of supporting a transition metal-containing nonmetallocene organic metallic compound on a treated carrier, which necessarily involves complicate preparation steps.
Chinese patent application Laid-Open No. CN1539856A discloses a process for supporting a nonmetallocene catalyst on a composite carrier, comprising the steps of (1) drying or baking a porous carrier (as the carrier) at 100 to 1000° C., under an inert atmosphere or under a reduced pressure for 1 to 24 hours to thermally activate same; (2) dissolving a magnesium compound in a tetrahydrofuran-alcohol mixing system to obtain a solution, and then adding the thermally activated porous carrier to the solution, to sufficiently react with each other at 0 to 60° C. under stirring to obtain a transparent system, upon filtration, washing, drying and suction drying, to obtain a composite carrier; or introducing into the transparent solution a non-polar organic solvent to sufficiently precipitate same, and then upon filtration, washing, drying and suction drying to obtain a composite carrier; (3) dissolving a nonmetallocene catalyst for olefin polymerization in a solvent, and then contacting same with the composite carrier or the modified carrier for 12 to 72 hours, upon filtration, washing, drying and suction drying, to obtain the supported nonmetallocene catalyst. According to this process, it is necessary to prepare the composite carrier at the first place and then contacting same with the catalyst solution.
Chinese patent application Laid-Open No. CN1789290A discloses a process for supporting a nonmetallocene catalyst with a high activity, comprising the steps of reacting a carrier with a chemical activating agent to obtain a modified carrier; dissolving a magnesium compound in a tetrahydrofuran-alcohol mixing system to obtain a solution, and then adding the modified carrier to the solution to conduct a react, upon filtration, washing, drying and suction drying, to obtain a composite carrier; dissolving a nonmetallocene catalyst for olefin polymerization in a solvent, and then reacting same with the composite carrier, upon filtration, washing, drying and suction drying, to obtain the supported nonmetallocene catalyst. According to this process, it is necessary to prepare the modified carrier at the first place and then reacting same with the magnesium compound to obtain the composite carrier and then contacting same with the catalyst solution.
Chinese patent application Laid-Open No. CN101423574A discloses a supported single site nonmetallocene catalyst component and the preparation process thereof, comprising the steps of (1) preparation of a magnesium chloride/silica carrier; (2) preparation of an alkyl aluminoxane/magnesium chloride/silica carrier; and (3) preparation of the supported single site nonmetallocene catalyst component. According to this process, it is necessary to prepare the composite carrier at the first place and then reacting same with the alkyl aluminoxane, and finally contacting same with the catalyst solution.
Most of the prior art olefin polymerization catalysts are metallocene catalyst-based, for example, those according to U.S. Pat. No. 4,808,561 and U.S. Pat. No. 5,240,894, Chinese patent application Laid-Open Nos. CN1344749A, CN1126480A, CN1307594A, CN1103069A, and CN1363537A, and U.S. Pat. No. 6,444,604, EP 0685494, U.S. Pat. No. 4,871,705 and EP0206794, and Chinese patent No. 94101358.8. Again, all of these applications relate to the technology of supporting a transition metal-containing metallocene catalyst on a treated carrier.
The catalyst prepared using anhydrous magnesium chloride as a carrier exhibits a high catalytic activity in the olefin polymerization, but this kind of catalyst is very brittle, prone to crush in the polymerization reactor, resulting in a poor polymer morphology. The catalyst supported on silica has an excellent flowability, useful to a fluidized-bed gas-phase polymerization, but the silica-supported metallocene and nonmetallocene catalyst shows a lowered catalytic activity. If magnesium chloride could be appropriately combined with silica, a catalyst with high catalytic activity, controllable granule size and good abrasion resistance may be obtained.
According to EP0260130, provided is a catalyst produced by supporting a metallocene or nonmetallocene transition metal compound onto a methyl aluminoxane-treated SiO2 carrier, wherein the nonmetallocene transition metal herein refers to ZrCl4, TiCl4 or VOCl3 only. According to this patent, it is preferred for the surface of the carrier to be treated with an organic magnesium compound or the mixture of a magnesium compound and an alkyl aluminum. However, the process involved is very complicated, necessitating a vast of production steps.
Chinese patent No. 200610026765.8 discloses a single site Ziegler-Natta catalyst for olefin polymerization. In this catalyst, a coordination group-containing salicylaldehyde or substituted salicylaldehyde derivative is used as the electron donor. The catalyst is produced by introducing a pre-treated carrier (for example, silica), a metallic compound (for example, TiCl4) and the electron donor into a magnesium compound (for example, MgCl2)/tetrahydrofuran solution and then post-treating the resultant.
Chinese patent No. 200610026766.2 is similar to this patent, and relates to an organic compound containing a hetero atom and use thereof for producing a Ziegler-Natta catalyst.
Chinese patent application Laid-Open No. CN101412766A discloses a process for producing a magnesium compound supported nonmetallocene catalyst, comprising the steps of contacting a magnesium compound with a nonmetallocene ligand, to obtain a contact resultant, and treating the contact resultant with a chemical treating agent selected from the group consisting of Group IVB metal compounds, to obtain the magnesium compound-supported nonmetallocene catalyst. The thus obtained catalyst exhibits a relatively higher activity, however, a poor polymer particle morphology, a rather lowered bulk density and a relatively increased amount of fine powders.
As can be seen from aforesaid, the prior art supported nonmetallocene catalyst suffers from such problems as a complicate supporting process, which generally involves multiple steps for treating the carrier before supporting the nonmetallocene complex, and a low olefin polymerization activity, wherein there is no easy way to adjust same. If one tries to increase the activity, he has to significantly increase the amount of the co-catalyst to be used, which is undesirable. Further, the prior art supported nonmetallocene catalyst has been produced by supporting a nonmetallocene complex onto a treated carrier, and therefore is problematic in stability.
Therefore, there still exists a need for a supported nonmetallocene catalyst, which can be produced in a simple way and in an industrial scale, free of the problems associated with the prior art supported nonmetallocene catalyst.